Retractable knife



FIG. 1 is a perspective view of the retractable knife showing my new design with the blade shown retracted;

FIG. 2 is a top plan view thereof;

FIG. 3 is a front elevational view thereof;

FIG. 4 is a right side elevational view thereof;

FIG. 5 is a left side elevational view thereof;

FIG. 6 is a rear elevational view thereof;

FIG. 7 is a bottom plan view thereof;

FIG. 8 is a perspective view of the retractable knife showing my new design with the blade shown extended;

FIG. 9 is a top plan view thereof;

FIG. 10 is a front elevational view thereof;

FIG. 11 is a right side elevational view thereof;

FIG. 12 is a left side elevational view thereof;

FIG. 13 is a bottom plan view thereof. 

The ornamental design for a retractable knife, as shown and described. 